1. Field of the Invention
The present invention relates to a starter magnet switch that permits/inhibits the supply of electric power to a starter motor.
2. Description of the Related Art
FIG. 11 is a cross-sectional view showing a conventional starter magnet switch, for example, as disclosed in Japanese Patent Application Laid-Open No. Hei 11-182390. In the figure, a switch case 2 is connected to one end portion of a cylindrical solenoid case 1. A pair of fixed contacts 3 and 4 are fixed at a given interval within the switch case 2. A pair of conductors 5 and 6 are electrically connected to the fixed contacts 3 and 4, respectively.
A cylindrical bobbin 7 is accommodated within the solenoid case 1. A coil 8 is held on the outer peripheral portion of the bobbin 7. A fixed iron core 9 is fixed within the solenoid case 1. The fixed iron core 9 includes a flange portion 9a which is in contact with an end surface of the bobbin 7 at the switch case 2 side and a cylindrical portion 9b which is inserted into the bobbin 7.
A movable iron core 10 that slidably reciprocates is inserted into the bobbin 7. One end portion of the movable iron core 10 is brought in or out of contact with the end surface of the cylindrical portion 9b. Also, the other end portion of the movable iron core 10 projects externally from the solenoid case 1. An opening spring 11 that urges the movable iron core 10 in a direction where the movable iron core 10 is dissociated from the fixed iron core 9 is disposed between the other end portion of the movable iron core 10 and the solenoid case.
One end portion of the movable iron core 10 is fixed with a rod 12 that extends axially of the movable iron core 10 and reciprocates together with the movable iron core 10. The rod 12 includes a large-diameter portion 12a fixed onto the movable iron core 10 and a small-diameter portion 12b adjacent to the large-diameter portion 12a.
FIG. 12 is a front view showing a leading portion of the rod 12 shown in FIG. 11, and FIG. 13 is a cross-sectional view taken along a line XIII--XIII of FIG. 12. The small-diameter portion 12b of the rod 12 is equipped with a holding member 13 that can reciprocate in an axial direction of the small-diameter portion 12b. The holding member 13 includes a flange portion 13a and a cylindrical portion 13b. A ring-shaped holding plate 14 is abutted against an end surface of the cylindrical portion 13b.
A plate-shaped movable contact 15, which is brought in or out of contact with the pair of fixed contacts 3 and 4, is supported by the rod 12. The movable contact 15 is disposed between the flange portion 13a and the holding plate 14. A contact spring 16 that urges the movable contact 15 toward the fixed contacts 3 and 4 is disposed between the large-diameter portion 12a of the rod 12 and the holding member 13.
An annular mounting groove 12c is defined in the outer periphery of the leading portion of the small-diameter portion 12b. The mounting groove 12c is equipped with a metallic C-shaped stopper (stopper ring) 17 that regulates the movement of the movable contact 15 toward the axial direction of the rod 12. The stopper 17 is hardened by quenching or the like. A washer 18 is inserted into the small-diameter portion 12b between the stopper 17 and the holding plate 14.
A cover 19 is made of a metal softer than that of the stopper 17 and inserted into the small diameter portion 12b between the washer 18 and the stopper 17. The cover 19 includes a ring portion 19a that intervenes between the stopper 17 and the washer 18 and a cover body 19b that surrounds the stopper 17. The cover body 19b is provided with a plurality of caulking portions 19c that are engaged with the stopper 17. With this structure, the stopper 17 is prevented from being disengaged from the small-diameter portion 12b.
In the conventional starter magnet switch structured as described above, because no means are provided for sufficient regulating the movement of the stopper 17 radially of the rod 12, there is a fear that the stopper 17 will move radially due to vibrations or the like. Then, where the stopper 17 is repeatedly moved, it will come into contact with the cover 19 made of soft iron material, to wear the cover 19 worn from the inside. As a result, there is a fear that the cover 19 may be damaged by use over a long period of time, and the stopper 17 may be come disengaged due to the damaged cover 19.
Also, because the caulking portions 19c are formed in the cover body 19b, there is a fear that portions 19d between the respective caulking portions 19c (FIG. 12) will expand radially, shortening the creepage distances between the fixed contacts 3, 4 as well as the movable contact 15 and the cover body 19b with the result that the cover body 19b and the fixed contacts 3, 4 as well as the movable contact 15 are short-circuited.